Cyanide Analysis (Free, Physiologically Available)
The environmental chemistry of cyanide is extremely complex. The cyanide chemistry associated with MGP wastes in the environment is of particular interest because a wide range of cyanide species can be present, and there can be a significant difference in toxicity observed among the species. This risk based approach to characterizing cyanide requires reliable analytical procedures that can delineate the cyanide species that are present into categories based on their relative toxicities. In addition, the use of specific analytical methods is often mandated for samples collected under various regulatory settings. For example, the USEPA Clean Water Act (CWA) regulations generally require the use of total and amenable cyanide procedures for National Pollutant Discharge Elimination Systems (NPDES) and Publicly Owned Treatment Works (POTW) discharge applications and the EPA's RCRA and CERCLA regulations generally specify the use of total cyanide. For MGP applications, where a risk-based corrective action approach is being utilized, the concentration of cyanide species that are bioavailable is often of interest.
Alpha offers the following cyanide analytical methods that can be used to determine cyanide species considered to be bioavailable:
Free Cyanide via EPA Method 9016
This procedure was initially developed with the Sediment Contaminant Bioavailability Alliance (SCBA), which was a consortium involving industry, utilities, government and consultants. This method was originally an ASTM procedure that has now been incorporated into EPA's SW-846 methods manual. This is a very good procedure specific for free cyanide (CN-, HCN), the species that represent the most risk and generally proportionally the smallest contribution to overall total cyanide present.
Physiologically Available Cyanide (PAC) via MCP Method
The Massachusett Contingency Plan (MCP) Physiologically Available Cyanide (PAC) method was originally developed with the initiative of the Massachusetts Natural Gas Council and the MassDEP. The impetus for developing the method was based on the need for a risk-based procedure for use with MGP applications. The objective was to develop a procedure that could model the amount of cyanide that would be converted into bioavailable forms under conditions present in the human stomach. MGP wastes containing cyanide are typically composed of a high percentage of the strongly-complexed iron cyanides as a result of the use of iron as a cyanide scavenger in the typical MGP process stream. The iron-complexed cyanides, however, are relatively low in toxicity and the use of an analytical procedure, that does not exclude them from the total cyanide concentration determined by the method, can greatly over-estimate the risk these wastes pose to human health.
The original 1996 protocol was produced by the combined efforts of Ogden Environmental & Energy Services (now AMEC), Boston Gas (now National Grid), Bay State Gas, NET Atlantic and MassDEP. This procedure was then reviewed, revised and reformatted by the MassDEP Data Quality Enhancement Workgroup in 2004 and then again in 2010 and released, together with the MCP Total Cyanide Method, as one of the MCP methods listed in the Compendium of Analytical Methods. This procedure is unique, in that it incorporates both positive and negative controls that insure that the sum of weakly-complexed cyanide species, ranging from free cyanides up to but not including iron cyanides, is accurately represented.
Alpha Analytical published the following peer-reviewed paper concerning cyanide analysis for MGP applications: "A Comparison of Commonly Used Cyanide Analytical Methodologies for Manufactured Gas Plant (MGP) Applications", by James F. Occhialini, James C. Todaro, Joseph Clements, James Roth, Elena Dayn, Tamara Burke Devine, William R. Swanson and Michael Rostkowski, published in the Journal of Environmental Forensics, Taylor & Francis Publishers, Volume 5, Number 2, June 2004.